Background: Studies show, guidelines state, and performance measures assert that antimicrobial prescribing for uncomplicated acute bronchitis is inappropriate. However, clinicians prescribe antimicrobials in over 60% of the 22.5 million acute bronchitis visits in the United States each year. Previous successful interventions, while epidemiologically rigorous, have only reduced the antimicrobial prescribing rate to 40% or 50%. It is unknown if the antimicrobial prescribing rate for acute bronchitis can be brought to near zero percent in actual practice while maintaining patient safety and satisfaction. Research Plan: Specific Aim 1 of this project is to develop an EHR-integrated algorithm for the diagnosis and treatment of adults with acute bronchitis with a goal of reducing the antimicrobial prescribing rate to near zero percent. Specific Aim 2 is to perform a controlled, continuously-monitored, implementation of an EHR-integrated diagnosis and treatment algorithm for acute bronchitis in a large, diverse primary care practice. We will use a multi-modal implementation - including computerized decision support, reporting tools, and clinician feedback - and quality improvement techniques to ensure adherence to the algorithm and reduce the antimicrobial prescribing rate to near zero percent. The primary outcome will be the antimicrobial prescribing rate for patients with acute bronchitis. Secondary outcomes will include patient symptoms, patient satisfaction, patient safety, and healthcare costs. To ensure the effective future dissemination of the algorithm and intervention, a major outcome will be the capture and description of the components that had the greatest effect on the antimicrobial prescribing rate. Specific Aim 2a is to develop an EHR-independent version of the algorithm and implementation method for use in clinics that do not have EHRs. Specific Aim 3 is to disseminate the algorithm and implementation method throughout an 11-clinic Primary Care Practice-Based Research Network and reduce the antimicrobial prescribing rate for acute bronchitis to near zero percent. Future Directions and Implications: In the future, we plan to broadly disseminate and continue to test the effectiveness and safety of the EHR-dependent and EHR-independent versions of the algorithm and implementation method. Development, demonstration, and broad dissemination of an effective algorithm to reduce antimicrobial prescribing to near zero percent for acute bronchitis has the potential to decrease adverse drug events, healthcare costs, and the prevalence of antimicrobial resistant bacteria in the United states. This project will also examine the effectiveness of a variety of tools for changing ambulatory practice that can generalize to other clinical conditions.